:root {
    --red:        #b3201e;
    --red-dark:   #7d1716;
    --paul:       #1e6dd6;
    --sarah:      #c0397a;
    --bg:         #fafaf7;
    --paper:      #ffffff;
    --line:       #d8d4cc;
    --ink:        #222;
    --good:       #1f8a3b;
    --bad:        #c0392b;
    --shadow:     0 1px 2px rgba(0, 0, 0, .06), 0 4px 12px rgba(0, 0, 0, .05);
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
    background: var(--bg);
    color: var(--ink);
    line-height: 1.45;
}

.back-home {
    margin: .75rem 1rem 0;
    font-size: .9rem;
}
.back-home a {
    color: var(--red);
    text-decoration: none;
}
.back-home a:hover {
    text-decoration: underline;
}

.banner {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1.25rem;
    padding: 1rem;
    background: var(--red);
    color: white;
    flex-wrap: wrap;
}

.banner h1 {
    margin: 0;
    font-size: clamp(1.5rem, 4vw, 2.4rem);
    letter-spacing: .08em;
    font-weight: 800;
}

.badge {
    background: var(--red-dark);
    color: white;
    padding: .4rem .75rem;
    border-radius: 4px;
    font-size: .75rem;
    font-weight: 700;
    line-height: 1.2;
    text-align: center;
}

main {
    max-width: 1100px;
    margin: 0 auto;
    padding: 1.5rem 1rem 3rem;
}

.instructions {
    background: var(--paper);
    border-left: 4px solid var(--red);
    padding: .9rem 1rem;
    box-shadow: var(--shadow);
    border-radius: 4px;
    margin-bottom: 1.5rem;
}

.paul  { color: var(--paul); }
.sarah { color: var(--sarah); }

/* ---- Buttons ---- */
button {
    padding: .65rem 1.2rem;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    background: var(--red);
    color: white;
    transition: background .15s, transform .05s;
}
button:hover  { background: var(--red-dark); }
button:active { transform: translateY(1px); }
button.secondary {
    background: white;
    color: var(--ink);
    border: 1px solid var(--line);
}
button.secondary:hover { background: #f0eee8; }

/* ---- Modal overlay ---- */
.exo-modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, .45);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9000;
    animation: exo-fade-in .15s ease;
}
@keyframes exo-fade-in { from { opacity: 0; } }
.exo-modal {
    background: var(--paper, #fff);
    border-radius: 12px;
    padding: 1.8rem 2rem 1.4rem;
    max-width: 400px;
    width: 90%;
    box-shadow: 0 8px 32px rgba(0,0,0,.25);
    text-align: center;
}
.exo-modal h3 { margin: 0 0 .5rem; color: var(--red); }
.exo-modal p  { margin: 0 0 1.2rem; line-height: 1.5; }
.exo-modal button {
    min-width: 120px;
}

/* ---- Result banner ---- */
.result {
    margin-top: 1.5rem;
    padding: 1rem 1.2rem;
    border-radius: 8px;
    background: var(--paper);
    box-shadow: var(--shadow);
    border-left: 4px solid var(--ink);
}
.result.hidden { display: none; }
.result.perfect { border-left-color: var(--good); background: #e7f6ec; }
.result h3 { margin: 0 0 .25rem; }

/* ---- Shared exercise components ---- */
.exo-actions {
    display: flex;
    flex-wrap: wrap;
    gap: .75rem;
    margin: 1.25rem 0 1rem;
    align-items: center;
}

.exo-leaderboard {
    margin-top: 2rem;
    background: var(--paper);
    padding: 1rem 1.2rem;
    border-radius: 8px;
    box-shadow: var(--shadow);
}
.exo-leaderboard h2 {
    margin: 0 0 .5rem;
    font-size: 1rem;
    text-transform: uppercase;
    letter-spacing: .05em;
    color: #666;
}
.exo-scores {
    margin: 0;
    padding-left: 1.4rem;
}
.exo-scores li {
    padding: .25rem 0;
    border-bottom: 1px dotted var(--line);
}
.exo-scores li:last-child { border-bottom: 0; }
.exo-scores .empty {
    color: #666;
    font-style: italic;
    list-style: none;
    margin-left: -1.4rem;
}
.exo-scores .score { font-weight: 700; color: var(--red); }
.exo-scores time   { color: #999; font-size: .85em; margin-left: .4rem; }

.hidden { display: none; }

/* =========================================================
   Hub (index)
   ========================================================= */

.hub-main {
    max-width: 1000px;
    margin: 0 auto;
    padding: 1.5rem 1rem 3rem;
}

.hub-grid {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1rem;
}

.hub-card {
    background: var(--paper);
    border: 1px solid var(--line);
    border-radius: 10px;
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: transform .12s, box-shadow .12s, border-color .12s;
}
.hub-card:hover {
    transform: translateY(-2px);
    border-color: var(--red);
    box-shadow: 0 2px 4px rgba(0,0,0,.08), 0 8px 20px rgba(179,32,30,.10);
}

.hub-link {
    display: grid;
    grid-template-columns: 1fr auto;
    grid-template-rows: auto auto auto;
    grid-template-areas:
        "title arrow"
        "level arrow"
        "file  arrow";
    column-gap: 1rem;
    align-items: center;
    padding: 1rem 1.1rem;
    color: var(--ink);
    text-decoration: none;
    height: 100%;
}

.hub-title {
    grid-area: title;
    margin: 0;
    font-size: 1.1rem;
    color: var(--ink);
}

.hub-level {
    grid-area: level;
    justify-self: start;
    margin-top: .35rem;
    background: var(--red);
    color: white;
    font-size: .7rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: .04em;
    padding: .15rem .5rem;
    border-radius: 3px;
}

.hub-file {
    grid-area: file;
    margin-top: .55rem;
    font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
    font-size: .78rem;
    color: #888;
}

.hub-arrow {
    grid-area: arrow;
    font-size: 1.6rem;
    color: var(--red);
    transition: transform .12s;
}
.hub-card:hover .hub-arrow { transform: translateX(4px); }

.hub-empty {
    color: #999;
    font-style: italic;
    text-align: center;
    padding: 2rem 0;
}

/* ===== Auth strip (top bar) ===================================== */
.auth-strip {
    display: flex;
    align-items: center;
    justify-content: flex-end;
    gap: .75rem;
    padding: .45rem 1rem;
    background: #1a1a1a;
    color: #eee;
    font-size: .85rem;
}
.auth-strip__who { color: #ccc; }
.auth-strip__who strong { color: #fff; }
.auth-strip__role { color: #888; margin-left: .25rem; font-weight: 400; }
.auth-strip__logout { margin: 0; padding: 0; }
.auth-strip__btn {
    background: transparent;
    color: #fff;
    border: 1px solid #555;
    border-radius: 4px;
    padding: .25rem .65rem;
    font: inherit;
    text-decoration: none;
    cursor: pointer;
    line-height: 1.2;
}
.auth-strip__btn:hover { background: #333; border-color: #888; }
.auth-strip__btn--link { color: #fff; }

/* ===== Auth pages (login / message / error) ===================== */
.auth-main {
    max-width: 520px;
    margin: 2rem auto;
    padding: 1.5rem 1rem 3rem;
}
.auth-card {
    background: var(--paper);
    border-radius: 10px;
    box-shadow: var(--shadow);
    padding: 1.6rem 1.4rem;
}
.auth-card h2 {
    margin: 0 0 .5rem;
    font-size: 1.3rem;
    color: var(--red-dark);
}
.auth-card p { margin: .4rem 0 .8rem; color: #444; }
.auth-form { display: flex; flex-direction: column; gap: .8rem; margin-top: 1rem; }
.auth-form label { font-weight: 600; font-size: .9rem; }
.auth-form__hint {
    margin: -.2rem 0 .2rem;
    font-size: .85rem;
    color: #666;
}
.auth-form input {
    padding: .6rem .8rem;
    border: 1px solid var(--line);
    border-radius: 6px;
    font-size: 1rem;
    background: white;
}
.auth-form input:focus {
    outline: none;
    border-color: var(--red);
    box-shadow: 0 0 0 3px rgba(179, 32, 30, .15);
}
.auth-form button {
    padding: .65rem 1rem;
    background: var(--red);
    color: white;
    border: 0;
    border-radius: 6px;
    font-weight: 700;
    font-size: 1rem;
    cursor: pointer;
}
.auth-form button:hover { background: var(--red-dark); }
.auth-flash {
    padding: .7rem .9rem;
    border-radius: 6px;
    margin-bottom: 1rem;
    font-size: .92rem;
}
.auth-flash--ok   { background: #e7f6ec; color: #1d6b32; border: 1px solid #b9e2c4; }
.auth-flash--err  { background: #fbe9e7; color: #8a2018; border: 1px solid #f1b8b2; }
.auth-flash--info { background: #eef2fb; color: #2a3d6b; border: 1px solid #c5d2ec; }
.auth-back { display: inline-block; margin-top: 1rem; color: var(--red); text-decoration: none; }
.auth-back:hover { text-decoration: underline; }

.auth-main:has(.teacher-students) { max-width: 760px; }
.teacher-students {
    width: 100%;
    border-collapse: collapse;
    margin-top: .8rem;
    font-size: .95rem;
}
.teacher-students th,
.teacher-students td {
    padding: .55rem .6rem;
    text-align: left;
    border-bottom: 1px solid var(--line);
    vertical-align: middle;
}
.teacher-students th {
    font-size: .78rem;
    text-transform: uppercase;
    letter-spacing: .04em;
    color: #666;
    background: #f7f5f0;
}
.teacher-students tr:last-child td { border-bottom: 0; }